Hi Andy
Your posting caught my notice because my Grandmother worked at Geraldra Station, Stockinbingal in the early years of the 20th Century. I know she was there in 1911, but had left by 1922 (she was born in 1891 so a little younger than your folk - perhaps she knew some of the children of Samuel?). I have a collection of photographs/postcards from her early years so will check for any Smedleys.
Did you know the NSW bdm records are online at
www.bdm.nsw.gov.au (follow the family history link). If you get a copy of a death certificate it should tell you the number of years spent in Australia (if the informant knew) which can give a likely time for arrival here. The cheapest option for this is via a transcription service - also detailed on the bdm site.
There is a record for William - father Thomas - death registered in 1892 District Wellington. Is Omigal part of Wellington? Wellington(Town) is in Western NSW between Dubbo and Orange - and I've just found that Ironbark is nearby - so that probably is your death record. I found 1 reference to Omigal via Google - it appears to be Goldrush country - 400km NW of Sydney. Also near Ironbark of AB (Banjo) Paterson fame.
http://www.stuarttown.org.au/(And I thought I knew the geography of NSW).
If your brothers spent their lives in Western NSW, local archives and newpaper records may well contain information on them, but there is little on the internet. Some emails to the local councils may help - this is the link to the Wellington library
http://www.wellington.nsw.gov.au/eservice/navigation.jspThe unassisted migrants have mention of a William and Samuel in 1855 - but age is given as C - I cannot find a code list - but C could mean child.
http://proarchives.imagineering.com.au/index_search.asp?searchid=23I can't find them on the NSW assisted immigrant list (and I don't think any NSW unassisted are online.) The archives site is
http://www.records.nsw.gov.au/ - I'm in Qld, so unlikely to get to the NSW archives. The NSW shipping gazette is online 1845-1855 - but no indexes - took me forever to go through looking for one of my family on a ship (and I still haven't found same).
http://www.nla.gov.au/ferg/issn/14403897.htmlTrish